This type of systems for leveling power supply and demand include a system using stationary batteries set in electricity consumers. This system charges the batteries during night when electricity demand is relatively low, and discharges the batteries during daytime when electricity demand is at its peak, thus leveling power supply and demand. Such a power supply and demand leveling system, which uses the stationary batteries, however, requires a large-scale installation. This makes it difficult to employ the system at low cost.
To solve this problem, it has lately been suggested to utilize a power supply and demand leveling system, which uses batteries installed in electric vehicles or hybrid electric vehicles (hereinafter, collectively referred to as electric vehicles) instead of using stationary batteries. The power supply and demand leveling system like this was made in light of the fact that an electric vehicle used for commuting to and from a business institution who is an electricity consumer remains parked during daytime when electricity demand is at its peak, and thus that there is a battery capacity available for use.
The system aims at leveling power supply and demand without large initial investment as in the case of using stationary batteries, by discharging batteries of electric vehicles parked on the premises of factories, businesses and the like by a charge/discharge command transmitted from a power supply/demand management center during demand peak periods, thereby compensating for deficiency of power supply, and charging them in the evening with low demand relative to power supply capacity, or in the night after returning home.
For example, patent document 1 proposes an example of control of charge and discharge of a battery by a charge/discharge command from a power supply/demand management center. In the power supply and demand leveling system disclosed in patent document 1, if the capacity of a battery of an electric vehicle parked is higher than a preset criterion, the battery is discharged to the preset criterion capacity for power supply and demand leveling.